ive just been hacked and i dont know what to do

hi,

my name is Assaf from Israel.

i need help plus i wanted to inform someone:

on the 12th of june i recieved an imessege from ***** (china),

written in chinese.

i opened it and did not reply. but thereafter i started receiving messeges saying that imesseges cost money.

moreover, that day i received an e-mail from apple saying:

"dear Assaf,

your Apple ID (***** ) was used to sign in to iMessage on an iMac 21.5" named “name的Mac”.

i tried to reset my password, and found it had been blocked. i only succeded reseting it today because it always said the operation timed out.

today i did it with my computer and it worked.

when i got into my account i saw this device connected, a 21.5" Mac named "name的Mac".

needless to say, it wasnt my device.

i removed it.

but now im worried whether i've been or stil am abused in some way and whether this thing can reoccur.

i couldn find an e-mail to send apple this..so here i go here.

whould be gratefull for help

thanks